Carbon fibers, which are lightweight and have properties such as high strength and high elastic modulus, have heretofore been used in carbon fiber-reinforced plastics. Already known as such carbon fiber-reinforced plastics are carbon composite materials which comprise carbon fibers arranged in unidirection and embedded in a matrix resin, for example, in a thermosetting resin or thermoplastic resin. These composite materials have a high strength axially of the carbon fibers. However, the strength (.sigma.T) in a direction orthogonal to the axial direction of the carbon fibers is dependent largely on the bond strength between the carbon fibers and the matrix resin, and is small and therefore differs greatly from the axial strength (.sigma.L), hence there is the problem that the material is great in so-called anisotropy (i.e., .sigma.L/.sigma.T). In other words, the composite material has a very high strength in the direction of the orientation of the fibers but has a relatively considerably low strength transverse to the orientation of the fibers. Accordingly, attempts have been made to diminish the anisotropy. For example, so-called unidirectionally reinforced sheets wherein fibers are arranged in parallel in one direction are superposed at varying angles to give an improved strength in a direction perpendicular to the orientation of fibers, or a fabric of carbon fibers is used to afford an improved strength in the direction perpendicular to the orientation of the fibers.
Further more, if the carbon fiber content in the above carbon composite material is adjusted to 70 vol. % or more in an attempt to impart a more improved strength to the material, voids will occur, resulting in a still lower strength in the direction orthogonal to the axes of the carbon fibers and eventually impairing the overall strength of the composite material. It is therefore difficult in the conventional carbon composite material to increase the proportion of carbon fibers for improving the strength, and to diminish anisotropy.
Accordingly, an object of the present invention is to provide a carbon composite material which is low in resin content and which nevertheless has a high mechanical strength and diminished anisotropy.
Another object of the invention is to provide a forming material for giving a carbon composite material which has such excellent characteristics and which is less likely to have voids and excellent in uniformity even when having a low resin content.